1. Field of the Invention
The present invention generally relates to heat lamps. More specifically, the present invention relates to heat lamps for improving the temperature uniformity in a field heated by one or more LED heat lamps.
2. Related Art
Chemical vapor deposition (CVD) is a very well known process in the semiconductor industry for forming thin films of materials on substrates, such as silicon wafers. In a CVD process, gaseous molecules of the material to be deposited are supplied to wafers to form a thin film of that material on the wafers by chemical reaction. Such formed thin films may be polycrystalline, amorphous or epitaxial. Typically, CVD processes are conducted at the elevated temperatures to accelerate the chemical reaction and to produce high quality films. Some processes, such as epitaxial silicon deposition, are conducted at extremely high temperatures ( greater than 900xc2x0 C.).
To achieve the desired high temperatures, substrates can be heated using resistance heating, induction heating or radiant heating. Among these heating techniques, radiant heating is the most efficient technique and, hence, is the currently favored method for certain types of CVD. Radiant heating involves positioning infrared lamps around a reaction chamber positioned within high-temperature ovens, called reactors. Unfortunately, radiant energy has a tendency to create nonuniform temperature distributions, including xe2x80x9chot spots,xe2x80x9d due to the use of localized radiant energy sources and consequent focusing and interference effects.
During a CVD process, one or more substrates are placed on a wafer support (i.e., susceptor) inside a chamber defined within the reactor (i.e., the reaction chamber). Both the wafer and the support are heated to a desired temperature. In a typical wafer treatment step, reactant gases are passed over the heated wafer, causing chemical vapor deposition (CVD) of a thin layer of the desired material on the wafer. If the deposited layer has the same crystallographic structure as the underlying silicon wafer, it is called an epitaxial layer. This is also sometimes called a monocrystalline layer because it has only one crystal structure. Through subsequent processes, these layers are made into integrated circuits, producing from tens to thousands or even millions of integrated devices, depending on the size of the wafer and the complexity of the circuits.
Various process parameters must be carefully controlled to ensure a high quality of layers resulting from CVD. One such critical parameter is the temperature of the wafer during each treatment step of wafer processing. During CVD, for example, the wafer temperature dictates the rate of material deposition on the wafer because the deposition gases react at particular temperatures and deposit on the wafer. If the temperature varies across the surface of the wafer, uneven deposition of the film occurs and the physical properties will not be uniform over the wafer. Furthermore, in epitaxial deposition, even slight temperature non-uniformity can result in crystallographic slip.
In the semiconductor industry, it is important that the material be deposited uniformly thick with uniform properties over the wafer. For instance, in Very Large and Ultra Large Scale Integrated Circuit (VLSI and ULSI) technologies, the wafer is divided into individual chips having integrated circuits thereon. If a CVD process step produces deposited layers with nonuniformities, devices at different areas on the chips may have inconsistent operation characteristics or may fail altogether.
The systems and methods of the present invention have several features, no single one of which are solely responsible for its desirable attributes. Without limiting the scope of this invention as expressed by the claims which follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled xe2x80x9cDetailed Description of the Preferred Embodiments,xe2x80x9d one will understand how the features of this invention provide several advantages over traditional CVD heating methods and systems.
One aspect is a chemical vapor deposition apparatus that comprises a high temperature processing chamber and a susceptor disposed within the chamber for supporting a wafer to be processed, the susceptor comprising a top surface, a bottom surface, and a perimeter. The apparatus further comprises a plurality of light emitting diodes (LEDs) located on a surface of the chamber, each configured to emit radiant energy towards the top surface, and a controller configured to adjust the radiant energy emitted by at least one of the plurality of LEDs relative to another one of the plurality of LEDs.
Another aspect is a method of processing a semiconductor in a chamber by applying heat from an array of LED lamps disposed adjacent to the chamber, each LED lamp being configured to emit directional radiant energy towards a substrate in the chamber. The method comprises inserting a wafer in a chamber, sensing an operational status of a plurality of LED lamps, if an LED from the plurality of LED lamps is non-operational, then adjusting a planned temperature profile for the plurality of LED lamps to compensate for the non-operational LED lamp. The method further includes applying heat from the plurality of LED lamps to the wafer, identifying nonuniformities in the temperature of the wafer, and adjusting an energy level output of at least one of the plurality of LED lamps with respect to another one of the plurality of LED lamps to compensate for the nonuniformity.
Still another aspect is a semiconductor processing apparatus that comprises a chamber defined by at least one wall, a structure, for supporting a substrate within the chamber, and at least one LED heat lamp array disposed proximate to the chamber.
Yet another aspect is an apparatus for processing semiconductor wafers at elevated temperatures that comprises a high temperature processing chamber defined by at least one wall, a susceptor disposed within the chamber for supporting a wafer to be processed, the susceptor comprising a top surface, a bottom surface, a perimeter, a first array of LED heat lamps being disposed proximate to the susceptor, and at least one LED lamp of the first array of LED heat lamps configured to emit directional radiant energy in a first direction towards the top surface. The apparatus further comprises a first perforated reflector located between the first array of LED heat lamps and the susceptor, the perforations being aligned with the at least one LED lamp of the first array and a second array of LED heat lamps being disposed proximate to the susceptor and parallel to the first array of LED heat lamps, the susceptor being disposed between at least a portion of the first array of LED heat lamps and said second array of LED heat lamps. The apparatus still further comprises at least one LED lamp of the second array of LED heat lamps configured to emit directional radiant energy in a second direction towards the bottom surface, both of the directions being at least partially disposed within a volume defined by the susceptor perimeter in a direction normal to the susceptor, and a second perforated reflector located between the second array of LED heat lamps and the susceptor, the perforations being aligned with the at least one LED lamp of the second array.
Another aspect is a chemical vapor deposition apparatus that comprises a process chamber having an area for horizontal positioning of a substrate within a substrate treatment zone and having chamber walls for conducting a flow of gas across a surface of the substrate, a first two-dimensional array of heat lamps being disposed generally above the substrate treatment zone, each LED of the first two-dimensional array of heat lamps having a length and a width so that the first two-dimensional array of heat lamps spans the substrate treatment zone in a first row and spans the substrate treatment zone in a first column generally perpendicular to the first row. The apparatus further comprises a first perforated reflector located between the first two-dimensional array of heat lamps and the substrate, the perforations being substantially aligned with the first two-dimensional array of heat lamps, a second two-dimensional array of heat lamps being disposed generally below said substrate treatment zone, each LED of the second two-dimensional array of heat lamps having a length and a width so that the second two-dimensional array of heat lamps spans the substrate treatment zone in a second row and spans the substrate treatment zone in a second column, at least one LED from the second row or second column having means for adjusting energy lamp output relative to another of the LEDs from the same second row or column, and a second perforated reflector located between the second two-dimensional array of heat lamps and the substrate, the perforations being substantially aligned with the second two-dimensional array of heat lamps.
Still another aspect is a method of processing a substrate in a chamber by applying heat from an LED lamp disposed adjacent to the chamber, the LED lamp being configured to emit directional radiant energy towards the substrate. The method comprises inserting a wafer in a chamber, applying heat from the LED lamp to the wafer, identifying nonuniformities in the temperature of the wafer, and adjusting an energy level output of the LED lamp to compensate for the nonuniformity.